1. Field of the Invention
The invention relates to the field of digital video tape recording and reproducing.
2. Description of the Related Art
The invention relates to a recording arrangement for recording an information signal in tracks on a record carrier, the recording arrangement including an input terminal for receiving the information signal and channel encoding apparatus for channel encoding the information signal to form a channel signal suitable for recording in a track on the record carrier. The recording arrangement also includes writing apparatus for writing the channel signal in the track. The channel signal includes multiple signal blocks which each include a first block section having a synchronization signal and a second block section which comprises a multitude of channel bytes. The invention also relates to a record carrier obtained with the recording arrangement, and to a reproducing arrangement for reproducing the video signal from the record carrier.
A recording arrangement as given in the opening paragraph is known from European Patent Application No. EP-A 492,704, corresponding to U.S. Pat. No. 5,245,483, reference (1).
The known recording arrangement is of the helical scan type and records an information signal, comprising a digital audio signal and a digital video signal, in audio signal recording sectors and video signal recording sectors, respectively, in multiple tracks. When recording a track, the video signal recording sector comes first and is followed by the audio signal recording sector. The order in which the sectors occur in a track can, however, also be in the reverse order. Furthermore, other sectors may be included in a track, such as, a clock run-in area, located at the beginning of a track, so as to enable a locking-in of the internal system clock on the signals read from the track, and preamble and postamble areas that are located between the various sectors and function as an edit gap. Reference is made in this respect to the earlier filed European Patent Application No. 93202950, corresponding to U.S. Pat. No. 5,424,878, reference (2) and European Patent Application No. 93201263, corresponding to U.S. Pat. No. 5,400,187, reference (3).
Reference is also made to: xe2x80x9cGrand Alliance HDTV Specificationxe2x80x9d, draft document, Feb. 22, 1994, reference (4); and to U.S. Pat. No. 5,142,421, reference (5).
These documents relate to proposals for a new digital video cassette (DVC) recorder standard, which enables the recording and reproduction of digital video and digital audio signals on/from a longitudinal magnetic record carrier. This new digital video recorder standard will lead to new digital video recorders and reproducers of the so-called DVC type. The above citations are hereby incorporated in whole by reference.
It is a object of the invention to provide a recording arrangement which is capable of recording other type of information signals in the known tape format as defined in the preamble. In the recording arrangement in accordance with a specific embodiment of the invention, the information signal is an MPEG information signal in accordance with an MPEG format, the MPEG information signal comprising multiple transport packets. Each time information is included in x transport packets of the MPEG information signal, the channel encoding apparatus stores the information included in the x transport packets of the MPEG information signal, into the second block sections of a group of y signal blocks of the channel signal. The second block section of at least the first signal block of the group of y signal blocks includes a third block section for storing identification information identifying the signal block as being the first signal block of the group of y signal blocks. Finally, x and y are integers such that xxe2x89xa71 and y greater than 1.
In a specific embodiment, the information signal is an MPEG information signal in accordance with an MPEG format, the MPEG information signal comprising multiple sequential transport packets. The channel encoding apparatus stores information included in x transport packets of the MPEG information signal into the second block sections of a group of y signal blocks of the channel signal. The second block sections of the signal blocks include a third block section for storing sequence number information relating to a sequence number of the signal blocks. Finally, x and y are integers such that xxe2x89xa71 and y greater than 1.
The invention is based on the following recognition. The draft Grand Alliance HDTV System Specification, dated Feb. 22, 1994, reference (4) above, more specifically, the chapters V and VI of this specification, includes a description of a transport system for transmitting an MPEG information signal. This signal includes a data compressed digital video signal and a corresponding data compressed digital audio signal, for broadcasting purposes or for transmission via a cable network. The MPEG information signal is in the form of transport packets having either an equal length or a variable length in time. In both cases, however, a transport packet comprises 188 bytes of information, the first byte being a synchronization byte.
A transmission of such an MPEG information signal, in the form of a recording on or a reproduction from a record carrier, such as a magnetic record carrier, requires that special measures be taken in order to accomplish such a transmission via the known tape format. More specifically, the invention relates to storing the transport packets in the signal blocks of the known tape format.
Generally, it can be said that, when storing the information included in a number of x transport packets of the MPEG information signal into a number of y signal blocks, some unoccupied space remains available in the y signal blocks which can be used for the storage of additional information. The additional information stored according to the invention, relates to the specific application of recording and reproducing the MPEG information signal on/from the record carrier. In a specific example of the DVC format, the second block sections may include 77 bytes of information. In that situation, two transport packets, from each of which the sync byte has been deleted, can be stored in second block sections of five signal blocks. Now, 11 bytes (=5xc3x9777xe2x88x922xc3x97187) remain available in the five signal blocks. These 11 bytes may be divided over the second block sections of the five signal blocks in various ways so as to obtain the third block sections. An example of one such way is that the first two bytes of all second block sections are made available as third block sections, and that the last of the 11 available bytes can be considered as a third block section for indicating the boundary between the information of the two transport packets as stored in the five signal blocks.
In the above example, identification information, identifying the signal block as being the first signal block of the group of y signal blocks, can be stored in a third block section of the first signal block in a group of y signal blocks. Alternatively, sequence number information (sequence numbers) relating to the sequence of the signal blocks may be stored in the third block sections. This sequence number may also be identified as a continuity counter. The measures proposed result in a number of advantages.
The advantage of storing identification information to identify a signal block as being the first signal block in a group of y signal blocks, is that the beginning of a group can be detected, which simplifies the read out of the data during reproduction.
One advantage of storing sequence numbers is that, when reproducing the signal blocks, it can be decided, upon retrieval of the sequence numbers, whether a signal block has been missed because of reproduction errors, so that an error correction or concealment can be carried out. Another advantage of storing sequence numbers is that one may shuffle the information to be stored into the signal blocks upon recording. Upon retrieval of the sequence numbers, it is possible to perform a corresponding de-shuffling in response to the sequence numbers retrieved so as to obtain the original datastream.
Furthermore, having sequence numbers included in the third block sections of the signal blocks, makes it possible to repeat signal blocks, in case a transport packet of the MPEG data stream stored into those signal blocks requires higher protection against errors that can occur during the recording and a subsequent reproduction process.
In another specific embodiment, as before, the information signal is an MPEG information signal in accordance with an MPEG format, the MPEG information signal including multiple transport packets. The channel encoding apparatus stores the information included in x transport packets of the MPEG information signal, in the second block sections of a first group of y first signal blocks of the signal blocks of the channel signal, so as to enable a normal play mode using video information stored in the first group of y first signal blocks during a normal play reproduction mode. In addition, the channel encoding apparatus also retrieves a trick mode video signal from the MPEG information signal, and stores the trick mode video signal into second block sections of a second group of z second signal blocks of the signal blocks of the channel signal, so as to enable a trick play mode using the video information stored in the second signal blocks. Also, the second block sections of at least one signal block, in each first and second group of first and second signal blocks, respectively, include a third block section for storing identification information indicating whether the group contains first signal blocks or second signal blocks. Finally, x, y and z are integers such that xxe2x89xa71, y greater than 1 and z greater than 1.
In a more specific embodiment, the information signal is an MPEG information signal in accordance with an MPEG format, the MPEG information signal including multiple transport packets. The channel encoding apparatus stores information included in x transport packets of the MPEG information signal into the second block sections of a group of y signal blocks of the channel signal. The second block sections of at least these signal blocks, in a group of y signal blocks that include the start of a transport packet, include a third block section for storing sequence number information relating to a transport packet sequence number corresponding to the transport packet having its start stored into the second block section of the signal block.
This enables both reproduction in a normal play mode using the first signal blocks, and reproduction in a trick play mode using the second signal blocks, in response to the detection of the information indicating the groups contain first signal blocks or second signal blocks, respectively.
In another specific embodiment, the second block sections of all signal blocks in each first and second group of first and second signal blocks, respectively, include a third block section for storing identification information indicating whether the group contains first signal blocks or second signal blocks.
In a more specific embodiment, the second block sections of a group of y signal blocks, each include a third block section for storing sequence number information relating to a transport packet sequence number corresponding to the transport packet for which information is stored in the signal block.
Storing a packet sequence number has advantages if an MPEG datastream is received having a constant bit-rate, and including a number of different video programs interleaved in the MPEG datastream. Generally, such a datastream has too high a bit-rate for recording the total datastream on the record carrier. The recording arrangement may include a program selector for retrieving one video program and the corresponding audio signal from the MPEG datastream, so as to obtain the MPEG information signal for recording. As information corresponding to only one video program, is included in a MPEG transport packet, such a program selector selects only those transport packets from the MPEG datastream that include information corresponding to the only video program. This means that some packets of the original MPEG datastream that were received are deleted. Upon reproduction, however, an MPEG video signal in accordance with the MPEG standard, however, now including only the one video program, should be regenerated. Such a regenerated datastream should have the transport packets that were selected during recording, at the same location, that is, in some way, dummy packets, corresponding to the packets deleted upon recording, must be inserted in the regenerated datastream. Upon recording, a sequence number is added to each transport packet that was received, i.e., also for the packets that will be deleted. The sequence numbers of the packets that are selected and stored, are stored in the third block section of the signal blocks in which the transport packets are stored. Upon reproduction, a sequence of numbers is retrieved, where each subsequent number retrieved will not necessarily be the next higher number. In that situation, one or more dummy packets must be inserted so as to regenerate the replica of the original MPEG datastream.
In another specific embodiment, the recording arrangement includes detection apparatus for detecting the moment of receipt of the transport packets and for generating timing information for each transport packet received. The timing information for a transport packet corresponds to the moment of receipt of the transport packet. The second block sections of at least those signal blocks in a group of y signal blocks that include the start of a transport packet, include a third block section for storing the timing information for the transport packet having its start stored in the second block section of the signal block.
In a more specific embodiment, the second block sections of a group of y signal blocks each include a third block section for storing the timing information corresponding to the transport packet which has information stored in the second block section of the signal block. Storing timing information corresponding to a transport packet, requires that the recording arrangement is provided with detection apparatus for detecting the time of receipt of a transport packet. This measure has advantages if an MPEG datastream is received having a variable bit-rate and including a number of different video programs interleaved in the MPEG datastream. As has been said above, generally, such datastream has too high a bit-rate for recording the total datastream on the record carrier. The recording arrangement includes a program selector for retrieving one video program with its corresponding audio signal from the MPEG datastream, so as to obtain the MPEG information signal for recording. As information corresponding to only one video program is included in a MPEG transport packet, such a program selector selects only those transport packets from the MPEG datastream that include information corresponding to the only one video program. By detecting and storing the timing information corresponding to a transport packet, the reproducing arrangement is capable of retrieving the timing information and recreating the MPEG information signal using the timing information.
It should be noted, that the measures (embodiments) discussed above can be applied solely or in combination with one another in the recording arrangement. As a result, record carriers will be produced having signal blocks stored in tracks on the record carrier. The signal blocks have a first block section which includes a synchronization signal and a second block section which includes a multitude of channel bytes. The x transport packets of the MPEG information signal are stored in the second block sections of a group of y signal blocks of the channel signal. Further, in accordance with the invention:
the second block section of at least the first signal block of the group of y signal blocks includes a third block section for storing identification information identifying the signal block as being the first signal block of the group of y signal blocks; or
the identification information is sequence number information and the second block sections of a group of y signal blocks all include a third block section for storing sequence number information relating to the sequence numbers of the signal blocks; or
the second block sections of the signal blocks each include a third block section for storing identification information indicating whether the signal block includes xe2x80x98normal playxe2x80x99 data or xe2x80x98trick modexe2x80x99 data; or
the second block sections of at least those signal blocks in a group of y signal blocks that include the start of a transport packet also include a third block section for storing identification information relating to a transport packet sequence number corresponding to the transport packet having its start portion stored in the second block section of the signal block; or
the second block sections of at least those signal blocks in a group of y signal blocks that include the start of a transport packet, also include a third block section for storing the timing information for the transport packet having its start in the second block section of the signal block; or
the third block sections include information resulting from a combination of one or more of the measures listed above.
It will be apparent that a reproducing arrangement will be needed which is adapted to each specific embodiment of the recording arrangement, so as to enable a reproduction of the MPEG information signal recorded on the record carrier. Such a reproducing arrangement is the subject of the claims directed to the reproducing arrangement.